DE102005006953A1 - Switchgear, for over-current protection, has polymer positive temperature coefficient element which gets expanded due to change to high impedance condition causing mechanical unlatching of latch, by which main contact is opened - Google Patents

Abstract

Switchgear has a pair of main contacts (3), whose movable switching contact (6) can be controlled over the switch latch (5). The expansion of the polymer positive temperature coefficient (PTC) element (4) occurring due to the change to the high impedance condition causes the mechanical unlatching of the switch latch, by which the pair of main contacts is opened.

Description

The The invention relates to a switching device with PTC element according to the preamble of claim 1. The invention can be used both in circuit breakers the house installation technology as well as with switching devices without overcurrent protection function be used.

From the EP 0 519 346 A1 is a circuit breaker with an overcurrent, in particular short-circuit current, responsive electromagnetic triggers, to whose trip coil a PTC resistor (resistor with positive temperature characteristic) is connected in parallel. This parallel circuit trip coil / PTC resistor is connected in series with a series resistor.

Generally known circuit breaker have a thermal and a magnetic trigger and are usually for AC usable. While the thermal trigger Time Lag works at low overcurrents, disconnects the magnetic trigger the contacts at short circuit currents after a short time.

at Current-limiting circuit breakers is the short-circuit current through one as possible fast onset and steep arc voltage rise strong limited, so that the prospective short-circuit current is not reached becomes. For this purpose, the arc is passed into a quenching chamber and into several Partial arcs divided up. The water process brings but also unwanted side effects with himself. The arc burdens the contacts as it forms of the switch. The arc voltage acts back into the network and the Size of voltage rise speed is crucial for the resulting frequency spectrum of interfering harmonics.

At the Use in DC systems, the same applies, but it is missing the deletion supportive Effect of the zero crossing of the mains voltage. It can be especially at small streams to "stop" the arc in the contact gap and subsequently to the destruction of the circuit breaker come. Therefore, for DC voltage modified devices with additional Devices for arc blowing (eg magnets) are used, whose connections of polarity must be assigned.

Of the Invention is based on the object, a switching device with PTC element indicate that the current exceeds a defined limit Limit current first is reduced to a small residual current and only then the main contacts open become.

These The object is achieved in conjunction with the features of the preamble according to the invention solved specified in the characterizing part of claim 1 features.

The particular advantages of the invention are that a load on the contacts of the switching device is avoided. Using of the switching device as a circuit breaker are a thermal release, a magnetic trigger or a quenching chamber not required, so that the manufacturing costs are reduced. There is no arc voltage generated by a switching operation back to the net and the harmonic load of the network is very low. The switching device is universal for direct current and AC suitable.

Further Advantages will be apparent from the following description.

advantageous Embodiments of the invention are characterized in the subclaims.

The Invention will be described below with reference to the drawing Embodiments explained. It demonstrate:

1 a switching device with overcurrent protection function,

2 a switching device without overcurrent protection function.

In 1 is a switching device with overcurrent protection function (circuit breaker) shown. Between a first clamp 1 and a second clamp 2 is the series connection of a main contact pair 3 and a polymeric PTC element 4 arranged. A switch lock 5 actuates the output side a movable switching contact 6 of the main contact pair 3 and is the input side via an actuator 7 (usually a manual shifter) and through the polymeric PTC element 4 acted upon.

In 2 is a switching device without overcurrent protection function shown. Between a first clamp 8th and a second clamp 9 is the series connection of a pre-contact pair 10 and a main contact pair 11 arranged. The connection point of both contact pairs 10 . 11 is with 12 designated. Parallel to the pre-contact pair 10 is a polymeric PCT element 13 arranged. A switch lock 14 actuates the output side a movable switching contact 15 of the pre-contact pair 10 and a movable switching contact 16 of the main contact pair 11 and is the input side via an actuator 17 (manual shift lever or contactor) and through the polymeric PTC element 13 acted upon.

• • Das polymere PTC-Element hat im Ausgangszustand einen kleinen Widerstand (niederohmiger Zustand), bei Stromerhöhung über einen definierten Grenzstrom steigt der Widerstand stark an (hochohmiger Zustand) und begrenzt damit den fließenden Strom auf einen geringen Reststrom. Das polymere PTC-Bauelement verbleibt solange in diesem hochohmigen Zustand, solange Spannung anliegt (und dieser Reststrom fließt). Nach Unterbrechung des Stroms wird das polymere PTC-Element nach einigen Sekunden wieder niederohmig.
• • Im Gegensatz zu keramischen PTC-Elementen haben polymere PC-Elemente sowohl eine höhere Betriebsspannung (250 V) als auch zusätzlich eine nutzbare reversible Volumenänderung bei der Widerstandsänderung. Diese Volumenänderung wird in vorliegendem Fall zur mechanischen Beaufschlagung des Schaltschlosses herangezogen.

Electrically conductive PTC elements (PTC thermistors) are known per se, for. B. Polymer based as PPTC (Polymeric Positive Temperature Coefficient) - elements. In electronic applications, polymeric PTC elements e.g. B. used as self-resetting fuses on thermistor base. For the proposal according to the invention, the following functions of a polymeric PTC element are of importance:

• • The polymeric PTC element has a small resistance in the initial state (low-resistance state), with current increase above a defined limiting current, the resistance rises sharply (high-resistance state) and thus limits the flowing current to a low residual current. The polymeric PTC device remains in this high-resistance state as long as voltage is applied (and this residual current flows). After interruption of the current, the polymeric PTC element becomes low again after a few seconds.
• • In contrast to ceramic PTC elements, polymeric PC elements have both a higher operating voltage (250 V) and, in addition, a usable reversible volume change in the resistance change. This volume change is used in the present case for mechanical loading of the switching mechanism.

• • thermischen Auslöser (Überstrom-Ausslösung) und
• • magnetischen Auslöser (Kurzschlussstrom-Auslösung).

The polymeric PTC element 4 replaced with the circuit breaker according to 1 the usual ones

• • thermal release (overcurrent release) and
• • magnetic release (short-circuit current tripping).

The volume change or expansion of the polymeric PTC element which occurs when the resistance changes (from the low-impedance to the high-resistance state) becomes mechanical for the unlatching of the switching mechanism 5 . 14 (and thus opening the contacts) used. The mechanical coupling / connection between PTC element 4 . 13 and switch lock 5 . 14 is set so that only after reaching the high-impedance state, the switch lock is unlatched, causing the contacts (main contact pair 3 with movable switching contact 6 respectively main contact pair 11 with movable switching contact 16 ) advantageously only have to interrupt the low residual current.

The switching device according to 2 is additionally with pre-contacts 10 / 15 equipped. The actuator 17 opens and closes the pre-contacts 10 / 15 (Vorkontaktpaar 10 with movable switching contact 15 ) and clamps when closing the main contacts 11 / 16 (Main contact pair 11 with movable switching contact 16 ) the switch lock 14 , The pre-contacts 10 / 15 bridge the PTC element 13 when they are closed and turn it into the power flow when they are open, so that then an electrical series circuit terminal 8th - PTC element 13 - connection point 12 - Main contacts 11 / 16 - clamp 9 results. After opening the Vorkontaktpaars 10 (due to a loading of the switch lock 14 over the actuator 17 ), the current is reduced to a small residual current and then only the main contact pair 11 opened (after the PTC element 13 extended and therefore the switch lock 14 has acted accordingly).

• 1. Beim Einschalten über Betätigungsorgan 17/Schaltschloss 14 werden zuerst die Vorkontakte 10/15 geschlossen, danach wird das Schaltschloss 14 gespannt und die Hauptkontakte 11/16 werden geschlossen.
• 2. Beim Ausschalten über das Betätigungsorgan 17, das als Schalthebel (Handbetätigung) oder z. B. als Magnetspule (Schütz) ausgeführt sein kann, werden nur die Vorkontakte 10/15 geöffnet. Dadurch wird das PTC-Element 13 in den Stromfluss eingeschaltet und vom Strom durchflossen, welcher über dem definierten Grenzstrom des PTC-Elementes liegt. Das PTC-Element erwärmt sich und gelangt in den hochohmigen Zustand, folglich sinkt der Strom bis auf den Reststrom. Mechanisch bewirkt die Ausdehnung (Volumenänderung) des PTC-Elementes 13 danach die Entklinkung des Schaltschlosses 14, wodurch die Hauptkontakte 11/16 geöffnet werden. Die mechanische Verbindung zwischen PTC-Element 13 und Schaltschloss 14 ist so eingestellt, dass erst nach Erreichen des Reststromes (und der damit verbundenen Ausdehnung) das Schaltschloss 14 entklinkt wird, wodurch die Hauptkontakte 11/16 vorteilhaft nur den Reststrom unterbrechen müssen.

The two operating modes of the switching device according to 2 "Switch on" and "switch off" can be described as follows:

• 1. When switching on actuator 17 / Latching mechanism 14 First, the pre-contacts 10 / 15 closed, then the switch lock 14 curious and the main contacts 11 / 16 will be closed.
• 2. When switching off via the actuator 17 , as a lever (manual operation) or z. B. can be designed as a magnetic coil (contactor), only the pre-contacts 10 / 15 open. This will make the PTC element 13 switched into the current flow and flows through the current, which is above the defined limit current of the PTC element. The PTC element heats up and enters the high-resistance state, as a result of which the current sinks to the residual current. Mechanically causes the expansion (volume change) of the PTC element 13 then the unlatching of the switch lock 14 , causing the main contacts 11 / 16 be opened. The mechanical connection between PTC element 13 and switch lock 14 is adjusted so that only after reaching the residual current (and the associated expansion) the switching mechanism 14 Unlatched, causing the main contacts 11 / 16 advantageous only have to interrupt the residual current.

In both embodiments according to 1 . 2 the PTC element operates equally on AC and DC.

1

first clamp

2

second clamp

3

Main contact pair

4

polymeric PTC element

5

switch lock

6

Portable Switching contact of the main contact pair

7

actuator

8th

first clamp

9

second clamp

10

Vorkontaktpaar

11

Main contact pair

12

junction both contact pairs

13

polymeric PTC element

14

switch lock

15

Portable Switch contact of the pre-contact pair

16

Portable Switching contact of the main contact pair

17

actuator

Claims (5)

Switching device with a main contact pair ( 3 . 11 ), whose movable switching contact ( 6 . 16 ) via a switch lock ( 5 . 14 ), wherein a polymeric PTC element ( 4 . 13 ) in series with the main contacts ( 3 / 6 . 11 / 16 ), whose ohmic resistance changes from a defined limiting current from the low-resistance state to the high-resistance state, whereby the current drops to a residual current, characterized in that the expansion of the polymeric PTC element occurring during the change into the high-resistance state ( 4 . 13 ) mechanically the unlatching of the switching mechanism ( 5 . 14 ), whereby the main contact pair ( 3 . 11 ) is opened. Switching device according to Claim 1, characterized by the series connection of a main contact pair ( 3 ) and a polymeric PTC element ( 4 ) between first and second terminals ( 1 . 2 ) of the switching device. Switching device according to claim 1, characterized by the series connection of a pre-contact pair ( 10 ) and a main contact pair ( 11 ) between first and second terminals ( 1 . 2 ) of the switching device, wherein the Vorkontaktpaar ( 10 ) a polymeric PTC element ( 13 ) is connected in parallel, which mechanically to a common switch lock ( 14 ) acting on the movable switching contacts ( 15 . 16 ) of the main contacts ( 11 / 16 ) and precontacts ( 10 / 15 ). Switching device according to claim 3, characterized in that when switching on an actuating member ( 17 ) of the switch lock ( 14 ) first the pre-contacts ( 10 / 15 ) and then the switch lock ( 14 ) and the main contacts ( 11 / 16 ) getting closed. Switching device according to claim 3, characterized in that when switched off via an actuating member ( 17 ) of the switch lock ( 14 ) only the pre-contacts ( 10 / 15 ) and then the extension of the PTC element ( 13 ) mechanically the unlatching of the switching mechanism ( 14 ), whereby the main contacts ( 11 / 16 ).